Hundreds of activists confronted riot police on Monday as South Korea and the United States launched a new round of trade talks in the shadow of North Korea's nuclear test.
An estimated 2,000 protesters banging drums and gongs staged scattered demonstrations in the southern resort town of Seogwipo on Jeju island, witnesses said.
Hundreds of activists, shouting "FTA kills us!", scuffled or staged shoving matches with police in an attempt to break through a tight police cordon around the beachfront hotel where the free trade agreement talks are being held.
No serious clashes were reported.
Both governments want a deal approved by their legislatures before US President George W Bush's trade promotion authority -- allowing him to fast-track an accord through Congress -- expires next June.
Three previous rounds have made relatively little headway and time is running out to meet a year-end unofficial deadline.
The two sides say a deal is especially important after the North's October 9 nuclear test, to lessen the economic impact and demonstrate the strength of the US-South Korean alliance.
But South Korea indicated it would take a tough line with US negotiators as well as with protesters.
The two sides tabled complex tariff offers, with the South Korean proposal focusing on non-sensitive sectors, a Seoul official told reporters on condition of anonymity.
"South Korea insisted it would not lift tariffs on cars or scrap its new medical policy," he said.
"We hope for some progress at this round by focusing on industrial goods," said South Korean delegation spokesman Han Dong-Man separately.
South Korean officials say the FTA will help Asia's fourth-largest economy increase exports and upgrade its industrial structure.
But defiant farmers, unionists and activists have vowed to stage daily protests against any market-opening measures that endanger jobs.
"We are ready to risk our lives to stop the free trade deal which will destroy our agricultural industry," Seo Jeong-Hee, head of the Korea Advanced Farmers Federation, told a press conference.
Any pact opening up agriculture would force half of the nation's 3.5 million farmers to leave the land, he said.
"Signing a free trade agreement with the US, the world's agricultural powerhouse, is ... the death penalty for Korean farmers," the Korean Peasants League said.
Police had helicopters and some 10,000 officers on stand-by. Shipping containers and concrete barriers were used to block approach roads.
The coastguard deployed six patrol boats and 20 rubber craft to keep them away activists who had manned around 30 small boats.
Seoul and Washington began negotiating in June on what would be the largest such accord for the United States since the North American Free Trade Agreement.
But the South's desire to protect its farmers from cheap imports has been a major obstacle, along with disputes over the automotive industry, pharmaceuticals and other sensitive sectors.
The two sides also differ on Seoul's desire for Washington to treat goods produced in Kaesong, a South Korean-built industrial estate just inside North Korea, as South Korean-made.
But experts quoted by Yonhap news agency Sunday said this issue was almost dead after the nuclear test.
The week's negotiations involve a total of 355 people. They are meeting in 18 sessions to try to come up with separate outlines of accord.
South Korea is the seventh-largest trading partner and seventh-largest export market for the United States.
Two-way trade was valued at 72 billion dollars in 2005, according to US figures.